A group communication system is a dedicated wireless communication system that is developed to meet users' demands for command and dispatch and applied in specific industries. In the group communication system, a large number of wireless users share a small number of wireless channels. With command and dispatch as main applications, the group communication system is a multi-purpose and highly efficient wireless communication system. The group communication system has a wide range of applications in fields such as government sectors, public safety, emergency communications, electricity, civil aviation, petrochemical industry and military affairs. The distinguishing feature between the group communication system and a public communication system lies in that the group communication system needs to have highly efficient command and dispatch performance, and requires its network to be highly reliable and secure.
In 3rd Generation Partnership Project (3GPP) LTE, the group communication system is referred to Group Communication Service Enabler (GCSE). FIG. 1 shows the system architecture of an LTE GCSE.
In order to make efficient use of resources of a mobile network, the 3GPP proposes Multimedia Broadcast Multicast Service (MBMS). The service is a technology that transmitting data from a data source to multiple target mobile terminals, achieves sharing of resources of the network (including core network and access network), and improves the utilization ratio of the network resources (especially air interface resources). The MBMS defined by the 3GPP enables not only low-speed message-class multicast and broadcast of plaintext, but also broadcast and multicast of high-speed multimedia services, thus providing various abundant video, audio and multimedia services. This undoubtedly conforms to the development trends of future mobile data and provides better service prospects for the development of 3G. FIG. 2 shows a diagram of MBMS architecture in LTE.
At present, the industry is discussing the possibility of implementing group communication by employing MBMS technology. For a specific group communication UE, a required Group Communication Service (GCS) may be received in any one of the following two modes: multicast and unicast. The multicast mode refers to receiving the GCS through an MBMS bearer. In this case, the UE needs to have MBMS receiving capability
In the research and practice of the prior art, it is found that the prior art has the following problems: when GCSs are transmitted through the MBMS bearers, simultaneous initiation of multiple GCSs may cause congestion or overload in the network. However, a GCS Application Server (GCS AS) is not aware of the congestion or overload in the network and cannot deal with the congestion or overload in time. Thereby, this causes the target UE fail to receive the required GCSs normally.